A fuel cell system (200) for providing electrical energy. The system (200) comprises a fuel cell stack (201), an anode subsystem (203) with a proportional valve (205) for dosing a volume of gas to be fed to the fuel cell stack (201), a purge valve (207) for discharging gas from the anode subsystem (203) into an exhaust-gas path (209) of the fuel cell system (200), and a control unit (211) for controlling the proportional valve (205) and the purge valve (207). The control unit (211) is configured to use an electrical control current that is fed to the proportional valve (205) to readjust for a purging operation to draw conclusions regarding a hydrogen concentration in a gas that is fed to the purge valve (207), wherein the control unit (211) is furthermore configured to adjust the fuel cell system (200) in a manner dependent on the determined hydrogen concentration.

A system and method of controlling water imbalance in an electrochemical cell is provided. The method includes determining a present water imbalance in the electrochemical cell by summing a water.sub.in and a water.sub.created less a water.sub.out. Water.sub.in represents an amount of water introduced into the electrochemical cell by an oxidant feed gas; water.sub.created represents an amount of water created by the electrochemical cell from the electrochemical reaction; and water.sub.out represents an amount of water discharged from the electrochemical cell by an oxidant exhaust gas. The method includes tracking a cumulative water imbalance during operation of the electrochemical cell by repeatedly determining the present water imbalance and continuing to sum the results during operation. And, the method also includes adjusting a flow rate of the oxidant feed gas entering the electrochemical cell based on the cumulative water imbalance.

A fuel cell system comprising: a fuel cell, a fuel gas supplier configured to supply fuel gas to an anode of the fuel cell, an oxidant gas supplier configured to supply oxidant gas to a cathode of the fuel cell, a humidity adjuster configured to adjust a relative humidity of the fuel gas and a relative humidity of the oxidant gas, and a controller, wherein the controller detects the relative humidity of the fuel gas at an anode inlet of the fuel cell, and the controller detects the relative humidity of the oxidant gas at a cathode outlet of the fuel cell, and wherein, based on detection results, the controller controls the humidity adjuster so that the relative humidity of the fuel gas at the anode inlet is higher than the relative humidity of the oxidant gas at the cathode outlet.

The inspection method for a fuel cell stack including a plurality of unit cells comprises: (a) operating a fuel cell system, including the fuel cell stack and an anode gas circulation flow path that is connected between an anode gas discharge port and an anode gas supply port of the fuel cell stack to circulate anode gas, under a predetermined liquid water accumulation condition to accumulate liquid water in the anode gas circulation flow path; (b) causing, after the step (a), the fuel cell system to stop and stand by until a predetermined restarting condition is satisfied; and (c) restarting, after the step (b), the fuel cell system to implement power generation by the fuel cell stack, and measuring voltage of each of the unit cells to detect a unit cell having negative voltage.

A system and method of controlling water imbalance in an electrochemical cell is provided. The method includes determining a present water imbalance in the electrochemical cell by summing a water.sub.in and a water.sub.created less a water.sub.out. Water.sub.in represents an amount of water introduced into the electrochemical cell by an oxidant feed gas; water.sub.created represents an amount of water created by the electrochemical cell from the electrochemical reaction; and water.sub.out represents an amount of water discharged from the electrochemical cell by an oxidant exhaust gas. The method includes tracking a cumulative water imbalance during operation of the electrochemical cell by repeatedly determining the present water imbalance and continuing to sum the results during operation. And, the method also includes adjusting a flow rate of the oxidant feed gas entering the electrochemical cell based on the cumulative water imbalance.

A voltage applying unit of a water detecting device applies, to a pair of electrodes, a voltage changing within an application range that includes a first voltage which is smaller than an electrolysis voltage of water and a second voltage which is larger than the electrolysis voltage of the water. A judging unit judges presence or absence of the water based on change in electric current measured by a current measuring unit when the voltage changing within the application range is applied to the pair of electrodes.

Various embodiments of the present disclosure are directed to methods and systems for determining at least one actual value of a controlled variable of a conditioning unit for a reactant of a fuel cell. In one example embodiment, the method steps for determining the at least one actual value of a controlled variable includes: measuring a measured value of the actual value of the at least one controlled variable, calculating a model value of the at least one controlled variable using a model of the conditioning unit, calculating a model value of the actual value of the at least one controlled variable using a sensor model, calculating a correction value for the at least one controlled variable, and calculating the actual value of the at least one controlled variable as the sume of the correction value and of the model value of the at least one controlled variable.

The present disclosure relates to a vessel for a fuel cell, a fuel cell system, and a method for maintaining a non-explosive atmosphere in a cavity of a vessel for a fuel cell. The vessel comprises a wall defining a cavity, and a catalyst. The cavity comprises a non-explosive atmosphere comprising predominantly hydrogen gas or predominantly oxygen gas. The cavity is configured to receive the fuel cell. The catalyst is in contact with the non-explosive atmosphere in the cavity and the catalyst is configured to convert hydrogen gas and oxygen gas into water.

The application relates to a novel module for electrolysis or co-electrolysis of water or of SOFC fuel cell, within which the forces necessary to compress the seals are decoupled from those necessary for the electrical contact elements that ensure the passage of current in the module.

An electrochemical fuel cell assembly comprises a fuel cell stack having a fuel delivery inlet and a fuel delivery outlet. The fuel cell stack further includes a number of fuel cells each having a membrane-electrode assembly and a fluid flow path coupled between the fuel delivery inlet and the fuel delivery outlet for delivery of fuel to the membrane electrode assembly. A fuel delivery conduit is coupled to the fuel delivery inlet for 10 delivery of fluid fuel to the stack. A bleed conduit is coupled to the fuel delivery outlet for venting fluid out of the stack. A variable orifice flow control device coupled to the bleed conduit configured to dynamically vary an amount of fluid from the fuel delivery outlet passing into the bleed conduit as a function of one or more of the control parameters: (i) measured fuel concentration; (ii) measured humidity; (iii) cell voltages of fuel cells in the 15 stack; (iv) impedance of fuel cells in the stack; (v) resistance of fuel cells in the stack. The variable orifice flow control device may be coupled to a recirculation conduit and may be configured to dynamically vary a proportion of fluid from the fuel delivery outlet passing into the bleed conduit as a function of the control parameters.